Methods of Etching Films with Reduced Surface Roughness

ABSTRACT

Provided are methods for etching films comprising transition metals which help to minimize higher etch rates at the grain boundaries of polycrystalline materials. Certain methods pertain to amorphization of the polycrystalline material, other pertain to plasma treatments, and yet other pertain to the use of small doses of halide transfer agents in the etch process.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.15/383,556, filed Dec. 19, 2016, which is a continuation of U.S. patentapplication Ser. No. 14/793,977, filed Jul. 8, 2015, now U.S. Pat. No.9,540,736, which claims priority to U.S. Provisional Application No.62/030,232, filed Jul. 29, 2014, the entire disclosures of which arehereby incorporated by reference.

TECHNICAL FIELD

Aspects of the present invention relates generally to methods of etchingfilms. In particular, aspects of the invention relates to etching filmscomprising transition metals for semiconductor devices.

BACKGROUND

Deposition of films on a substrate surface is an common process in avariety of industries including semiconductor processing, diffusionbarrier coatings and dielectrics for magnetic read/write heads. Chemicalvapor deposition (CVD) and atomic layer deposition (ALD) are twodeposition processes used to form or deposit various materials on asubstrate. In general, CVD and ALD processes involve the delivery ofgaseous reactants to the substrate surface where a chemical reactiontakes place under temperature and pressure conditions favorable to thethermodynamics of the reaction. Additionally, in the semiconductorindustry, miniaturization benefits from atomic level control of thinfilm deposition to produce conformal coatings on high aspect structures.One method for deposition of thin films with control and conformaldeposition is atomic layer deposition (ALD), which employs sequential,surface reactions to form layers of precise thickness. Most ALDprocesses are based on binary reaction sequences which deposit a binarycompound film. Because the surface reactions are sequential, the two gasphase reactants are not in contact, and possible gas phase reactionsthat may form and deposit particles are limited.

However, before the present invention, there has not been a commerciallyavailable way to delicately etch films with control and conformality.For example, while there have been wet etch methods proposed for cobalt,there is still a need for dry methods to remove cobalt and/or cobaltresidue, and preferably in situ methods that are self-limiting and allowfor precise control over etch rate. Even more particularly, there is aneed for a method that is selective for a particular metal, which wouldprovide even more control over the etching process.

SUMMARY

One aspect of the invention pertains to a method of etching a substrate,the method comprising:

providing a polycrystalline film comprising a transition metal;

amorphizing at least a portion of the polycrystalline film to provide anamorphous layer;

exposing the amorphous layer to a halide transfer agent to provide anactivated substrate surface; and

exposing the activated substrate surface to a reagent comprising a Lewisbase or pi acid to provide a vapor phase coordination complex comprisingone or more atoms of the transition metal coordinated to one or moreligands from the reagent.

Another aspect of the invention pertains to a method of etching asubstrate, the method comprising:

providing a polycrystalline film comprising a transition metal;

exposing the polycrystalline film to an inert plasma, reducing gas orreagent vapor;

exposing the polycrystalline film to a halide transfer agent to providean activated substrate surface; and

exposing the activated substrate surface to a reagent comprising a Lewisbase or pi acid to provide a vapor phase coordination complex comprisingone or more atoms of the transition metal coordinated to one or moreligands from the reagent.

Another aspect of the invention pertains to a method of etching asubstrate, the method comprising:

activating a substrate surface comprising a polycrystalline film of ametal selected from the group consisting of Co, Cu, Ru, Ni, Fe, Pt, Mnand Pd, wherein activation of the substrate surface comprises exposingthe substrate surface to Br₂ or Cl₂ to provide an activated substratesurface; and

exposing the activated substrate surface to a reagent comprising TMEDAto provide a vapor phase coordination complex comprising one or moreatoms of the Co, Cu, Ru, Ni, Fe, Pt, Mn or Pd coordinated to one or moreligands from the reagent, wherein the Br₂ is present in an amounteffective to etch about one Angstrom of the substrate surface.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings.However, the appended drawings illustrate only typical embodiments ofthis invention and are therefore not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

FIG. 1 shows a schematic of a method in accordance with one or moreembodiments of the invention;

FIG. 2 shows a schematic of a method in accordance with one or moreembodiments of the invention; and

FIGS. 3A-B show TEM photographs of a film etched using a comparativemethod and a film etched using a method in accordance with one or moreembodiments of the invention, respectively.

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the invention, it isto be understood that the invention is not limited to the details ofconstruction or process set forth in the following description. Theinvention is capable of other embodiments and of being practiced orbeing carried out in various ways. It is also to be understood that thecomplexes and ligands of the present invention may be illustrated hereinusing structural formulas which have a particular stereochemistry. Theseillustrations are intended as examples only and are not to be construedas limiting the disclosed structure to any particular stereochemistry,unless otherwise indicated. Rather, the illustrated structures areintended to encompass all such complexes and ligands having theindicated chemical formula.

Etching processes can result in a very uneven surface post-etch.Resulting surfaces may have a pitted and rough surface, or with a smoothbut uneven surface. If the layer to be etched has crystalline grains theetch effects may be exacerbated at grain boundaries. Therefore a roughsurface may result, which may not be suitable for certain semiconductorapplications. While not wishing to be bound to any particular theory, itis thought that the varying etch rates is most likely due to deeperpenetration of certain reagents (i.e., halide) into the boundaries.Depending on the type of substrate and the how the etch process iscarried out one of the reagents, often a halogen-containing reagent, canmigrate much further into the bulk of the film. This tendency topenetrate the film is accentuated by certain film defects, differingcrystal faces and grain boundaries. It has been discovered that certaintreatments before and during the etch process, or certain modificationsto the etch process, can have the advantage of minimizing the differingetch rates. Such processes also result in smooth, conformal etchedsurfaces.

Accordingly, one aspect of the invention pertains to a method of etchinga substrate. First, a polycrystalline film comprising a transition metalis provided. The method also comprises amorphizing at least a portion ofthe polycrystalline film to provide an amorphous layer. Then, theamorphous layer may be exposed to a halide transfer agent to provide anactivated substrate surface. The activated substrate surface may then beexposed to a reagent comprising a Lewis base or pi acid to provide avapor phase coordination complex comprising one or more atoms of thetransition metal coordinated to one or more ligands from the reagent.

A “substrate” as used herein broadly covers polycrystalline filmscomprising one or more transition metals. In one or more embodiments,the substrate surface comprises at least one transition metal. In one ormore embodiments, the transition metal comprises a first row transitionmetal. In one or more embodiments, the polycrystalline film comprises ametal selected from the group consisting of Co, Cu, Ru, Ni, Fe, Pt, Mnand Pd. In some embodiments, the substrate surface consists essentiallyof the transition metal. In one or more embodiments, the substratesurface may comprise more than one transition metal, including metalalloys. An example of such a substrate includes a substrate comprisingboth cobalt and iron. In other embodiments, the substrate surfacecomprises at least one transition metal, but also comprises othercomponents. Other components may include carbon. In one or moreembodiments, the substrate surface comprises about 90 to about 100%transition metal and 0 to about 10% carbon. Carbide films may beespecially seen in embodiments relating to the removal of transitionmetal carbides deposited onto deposition chamber walls, showerheads, andother equipment components. In some embodiments, the other componentsmay include oxygen, boron, sulfur and/or nitrogen. Therefore, otherexamples of suitable substrate comprise materials include metalalloys/intermetallics, metal oxides, metal borides, metal sulfides,metal nitrides, metal intermetallic borides, metal intermetallic oxides,metal intermetallic sulfides and metal intermetallic nitrides. To beclear, the above encompasses substrate comprising more than onetransition metal as well as additional components. An example of such amaterial is a substrate comprising cobalt, iron and boron (CoFeB).

In some embodiments, the term includes equipment that has a layer ofbuildup deposited thereon. A common problem with one or more of thesedeposition processes is the unwanted deposition onto deposition chamberwalls, showerhead, etc. Thus, in some embodiments, the substratecomprises deposited metal overlying a deposition chamber wall, adeposition showerhead, etc. In one or more embodiments, the term refersto any substrate or material surface comprising a transition metal thatis formed on a second substrate upon which film processing is performedduring a fabrication process. Substrates may be exposed to apretreatment process to polish, etch, reduce, oxidize, hydroxylate,anneal and/or bake the substrate surface.

The term “substrate surface” refers to an exposed surface of thesubstrate. In one or more embodiments, and as the context dictates, aslayers are added to the substrate or (in the alternative) part of thesubstrate is removed, the newly exposed surface becomes the substratesurface.

As discussed above, amorphization is used to achieve more conformaletching. As used herein “amorphization” refers to a process ofconverting at least part of a polycrystalline material into an amorphousone (i.e., one with no long-range order). In one or more embodiments,amorphization comprises exposing the polycrystalline film to a plasma.In further embodiments, the plasma utilized is a direct plasma of Ar orH₂. The depth of amorphization can be controlled by varying the time andintensity of the plasma according to known methods. Another example of asuitable plasma includes an inert gas plasma (e.g., N₂).

In one or more embodiments, exposing the amorphous layer to the halidetransfer agent and exposing the activated substrate surface to thereagent etches the amorphous layer, and the amorphous layer is partiallyetched.

In some embodiments, exposing the amorphous layer to the halide transferagent and exposing the activated substrate surface to the reagent etchesthe amorphous layer, and the amorphous layer is substantially etched. Asused herein, “substantially etched” refers to at least 90, 95, 98, 99 or100% removal. In such a method, a process regime can be used in whichthe etch rate of amorphous material is much higher than the etch rate ofpolycrystaline material. In this case, the etch rate would be controlledby the depth of the amorphous layer and a smooth film will be obtained.

In one or more embodiments, the method further comprises repeatingexposing the amorphous layer to the halide transfer agent and exposingthe activated substrate surface to the reagent. In further embodiments,the polycrystalline film is amorphous more than a targeted amount, or asdeeply as possible (e.g., ˜5 to 10 nm). Then only a part of theamorphous layer is etched, and the etch depth is controlled using theknown etch rate of amorphous Co rather than relying on a self-limitedstop on the crystalline film.

Several processes will be exemplified below and in the figures. It is tobe understood that the structures shown are representative of thechemical mechanisms that are thought to be occurring during the etchprocess. However, they are not intended to be limiting, and otherchemical structures may occur.

FIG. 1 illustrates an exemplary process in accordance with one or moreembodiments of the invention. Specifically, an etching process usingamorphization is shown. First, a substrate of polycrystalline cobalt 100is provided. The surface is exposed to a plasma (e.g., Ar plasma) whichprovides an amorphous region 110. The amorphous region 110 is thenetched, leaving behind etched polycrystalline substrate 120. The etchingprocess can be carried out, for example, by exposing the amorphousregion 110 to Br₂ and TMEDA as discussed above.

FIG. 2 illustrates another process similar to FIG. 1, but insteaddemonstrates only partial removal of the amorphous region. First, apolycrystalline substrate 200 is provided. Again, the polycrystallinesubstrate 200 is exposed to a plasma (e.g., Ar), which provides anamorphous region 210. The amorphous region 210 may be thicker thanamorphous region 110. A part of amorphous region 210 is then etchedleaving behind a remainder of the amorphous region 220 overlying thepolycrystalline substrate 200. As with the process of FIG. 1, theetching process can be carried out, for example, by exposing theamorphous region 210 to Br₂ and TMEDA as discussed above.

Once an amorphous layer has been provided, all or part of the amorphouslayer may be etched. Etching may be accomplished by first activating asurface of the amorphous layer, which may be done through exposure to ahalide transfer agent, and then exposing a surface of the amorphouslayer to a Lewis base or pi acid.

In accordance with one or more embodiments of the invention, thereagents comprise a Lewis base or pi acid. A “pi acid,” as used herein,refers to a compound that, as a ligand, can accept electron density froma metal into empty pi orbitals as well as donate electron density to themetal via a sigma bond. A “Lewis base,” as used herein, refers to acompound that, as a ligand, can donate an electron pair to a metal.There are several suitable reagents for the processes described herein.

In one or more embodiments, the Lewis base or pi acid comprises achelating amine. In some embodiments, the chelating amine has astructure represented by:

wherein each R^(a) is independently hydrogen or C1-C4 alkyl group withthe proviso that not all of the R^(a) groups are hydrogen. In furtherembodiments, the chelating amine is selected from the group consistingof N,N,N′,N′-tetramethylethylene diamine (also known as TMEDA), ethylenediamine, N,N′-dimethylethylenediamine, 2-(aminomethyl)pyridine,2-[(alkylamino)methyl]pyridine, and 2-[(dialkylamino)methyl]pyridine,wherein the alkyl group is a C1-C6 alkyl group.

In some embodiments, the Lewis base or pi acid comprises CO,alkylphosphines (PR¹ ₃, wherein each R¹ is a C1-C6 alkyl group),1,2-bis(difluorophosphino)ethane, N₂O, NO, NH₃, NR² ₃, wherein each R²is independently hydrogen or C1-C6 branched or unbranched, substitutedor unsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomicgroup, or a compound having the structure:

wherein each R^(b) is independently hydrogen, R or C1-C4 alkyl. It isnoted that N₂O is not a traditional Lewis base, but does have a loneelectron pair. In some embodiments, wherein the reagent comprises NR² ₃,each R² is independently C1-C6 alkyl. In other embodiments, at least oneof the R² groups is cyclohexylamine.

In one or more embodiments, the pi acid comprises an aluminum precursor.In further embodiments, the aluminum precursor has formulaAlH_(n)X_(m)R^(c) _(p), wherein X is a halogen, the sum of n+m+p is 3,and R^(c) is C1-C6 alkyl.

In one or more embodiments, the process includes activation of thesubstrate surface. In some embodiments, activation of the substratesurface provides a surface termination which will react with a Lewisacid and/or pi acid. In further embodiments, the surface terminationwill react with any one or more of the Lewis acids and/or pi acids.

In some embodiments, exposure to the substrate surface comprisesexposing the substrate surface to a halide transfer agent. In one ormore embodiments, exposure of the substrate surface to the halidetransfer agent and any pi acid and/or Lewis base occurs sequentially orsubstantially sequentially As used herein, the phrase “exposure of thesubstrate surface to the halide transfer agent and the reagent occursubstantially sequentially” means that the substrate surface is exposedto the halide transfer agent with a majority of the halide transferagent exposure duration not coinciding with exposure to the reagent,although there may be some overlap. In some embodiments, exposure of thesubstrate surface to the halide transfer agent and any pi acid and/orLewis base occurs simultaneously or substantially simultaneously. Asused herein, “substantially simultaneously” means that the substratesurface is exposed to the halide transfer agent with a majority of thehalide transfer agent exposure duration coinciding with exposure to thereagent, although there may be some time where the two do not overlap.Again, while not wishing to be bound to any particular theory, it isthought that exposure of the substrate surface to a halide transferagent results in the substrate surface having halide surfaceterminations, which makes the substrate surface more reactive to one ormore of the pi acids and/or Lewis bases described herein. In someembodiments, the halide transfer agent comprises a dihalide. In furtherembodiments, the dihalide comprises I₂, Br₂, Cl₂. In other embodiments,the halide transfer agent comprises a trialkylsilyl halide or an alkylhalide, wherein the alkyl group(s) of either the trialkylsilyl halide oralkyl halide may be a C1-C6 alkyl group. Examples of suitable alkylhalides include ethyliodide and diiodoethane.

The substrate surface will therefore be at least one atomic layerthinner than before the etch process. In some embodiments, the etchprocess is self-limiting. That is, each time an etch cycle is performed,the same amount of the substrate is removed, although not necessarily atthe monolayer. For example, a certain number of Angstroms (e.g., about7), or several monolayers may be removed per cycle. In theseembodiments, one or more layers of transition metal atoms may bereliably removed each cycle. Such a method may be referred to as“alternating exposure etching,” where the substrate surface issequentially or substantially sequentially exposed to reagent andactivation agents. As used herein “substantially sequentially” meansthat the majority of the duration of the pulses does not overlap withthe pulse of co-reagent, although there may be some overlap. In otherembodiments, the process may be self-limiting at the monolayer. That is,in such embodiments, only one layer of transition metal atoms is removedat a time. Such a process may be referred to as “atomic layer etching.”

The specific reaction conditions for the etch reactions may be selectedbased on the properties of the reagents and substrate surface, as wellas the pressure used. The etch may be carried out at atmosphericpressure, but may also be carried out at reduced pressure. The substratetemperature should be high enough to keep the formed metal complexes inthe gaseous phase and to provide sufficient energy for surfacereactions. The properties of the specific substrate, film precursors,etc. may be evaluated using methods known in the art, allowing selectionof appropriate temperature and pressure for the reaction.

In some embodiments, the substrate surface temperature is kept belowabout 500, 475, 450, 425, 400, 375, 350, 325, or 300° C. In embodimentswhere the etch is utilized for cleaning buildup off of equipment, thesubstrate temperature may be kept below 250, 225, or 200° C. Thesubstrate surface temperature should be at least about room temperature(23° C.) or at least about 25, 50 or 75° C.

Therefore, once the substrate is activated and a reagent gas has beenflowed over the reactive surface, it is thought that the reagent gasforms a metal coordination complex with one or more of the transitionmetal atoms from the substrate surface. Ideally, the reaction conditionsare chosen so that the formed coordination complex is volatile at agiven temperature (i.e., in the vapor phase). Then, the complex maysimply be flowed away from the substrate surface and, as appropriate,out of the chamber. That is, in some embodiments, the method furthercomprises purging the vapor phase coordination complex.

Another aspect of the invention also pertains to a method of etching asubstrate. The method comprises providing a polycrystalline filmcomprising a transition metal. The method also comprises exposing thepolycrystalline film to an inert plasma, reducing gas or reagent vapor.The method may then comprise exposing the polycrystalline film to ahalide transfer agent to provide an activated substrate surface. Themethod may also comprise exposing the activated substrate surface to areagent comprising a Lewis base or pi acid to provide a vapor phasecoordination complex comprising one or more atoms of the transitionmetal coordinated to one or more ligands from the reagent.

While not wishing to be bound to any particular theory, it is thoughtthat by periodically treating the material being etched with a reducinggas, plasma or reagent vapor the excess halogen can be removed from thefilm and a low surface roughness etch achieved. In addition to periodictreatment adding a pre-etch treatment can ensure a low surface roughnessby removing surface oxidation. This periodic treatment can also removeresidual etch residues from the etched surface. The pre-treatment andperiodic treatment reagent can consist of mixtures and/or plasmas of thefollowing H₂, N₂, NH₃, Ar, He. The treatment may also consist ofmixtures of gases such as H₂, N₂, Ar, He with silyl amines. In furtherembodiments, such silyl amines include, but are not limited to,1,4-bis(trimethylsilyl)-1,4-diaza-2,5-cyclohexadiene

Exposure of the polycrystalline film to the inert plasma may thereforebe carried out just once or multiple times. In some embodiments,exposure of the polycrystalline substrate to the inert plasma may occurbefore any of the polycrystalline substrate has been etched.Alternatively, or additionally, exposure of the polycrystallinesubstrate to the inert plasma may occur after some etching has takenplace. The exposure of the polycrystalline substrate to the inert plasmamay be repeated after a given number of etch cycles (e.g., every 30cycles).

Any of the reagent, condition or substrate variations discussed abovemay be applied to this method, unless otherwise indicated. For example,in one or more embodiments, the Lewis base or pi acid comprises CO, PR¹₃, wherein each R¹ is independently a C1-C6 alkyl group,1,2-bis(difluorophosphino)ethane, N₂O, NO, NH₃, NR² ₃, wherein each R²is independently hydrogen C1-C6 branched or unbranched, substituted orunsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic group,or a compound having the structure:

wherein each R^(b) is independently hydrogen, R or C1-C4 alkyl. In someembodiments, the pi acid comprises AlH_(n)X_(m)R^(c) _(p), wherein X isa halogen, the sum of n+m+p is 3, and R^(c) is C1-C6 alkyl. In one ormore embodiments, the Lewis base or pi acid comprises a chelating amineselected from the group consisting of N,N,N′,N′-tetramethylethylenediamine, ethylene diamine, N,N′-dimethylethylenediamine,2-(aminomethyl)pyridine, 2-[(alkylamino)methyl]pyridine, and2-[(dialkylamino)methyl]pyridine, wherein the alkyl group is C1-C6alkyl.

In one or more embodiments, the halide transfer agent is selected fromthe group consisting of Cl₂ and Br₂. In some embodiments, thepolycrystalline film comprises cobalt. In one or more embodiments, thepolycrystalline film comprises a metal selected from the groupconsisting of Co, Cu, Ru, Ni, Fe, Pt, Mn and Pd. In some embodiments,the plasma comprises H₂, N₂, NH₃, Ar and/or He.

Another aspect of the invention pertains to yet another method ofetching a substrate. This method comprises activating a substratesurface comprising a polycrystalline film of a metal selected from thegroup consisting of Co, Cu, Ru, Ni, Fe, Pt, Mn and Pd, whereinactivation of the substrate surface comprises exposing the substratesurface to Br₂ or Cl₂ to provide an activated substrate surface. Next,the method may comprise exposing the activated substrate surface to areagent comprising TMEDA to provide a vapor phase coordination complexcomprising one or more atoms of the Co, Cu, Ru, Ni, Fe, Pt, Mn or Pdcoordinated to one or more ligands from the reagent, wherein the Br₂ ispresent in an amount effective to etch about one Angstrom of thesubstrate surface. While not wishing to be bound to any particulartheory, it is thought that in such processes, the halide dose is reducedto a relatively small volume in which the halide is depleted on thesurface and no excess remains to penetrate the grain boundaries. Thetime and pulse length may be varied to achieve the targeted etch rate.

In some processes, the use of plasma provides sufficient energy topromote a species into the excited state where surface reactions becomefavorable and likely. Introducing the plasma into the process can becontinuous or pulsed. In some embodiments, sequential pulses ofprecursors (or reactive gases) and plasma are used to process a layer.In some embodiments, the reagents may be ionized either locally (i.e.,within the processing area) or remotely (i.e., outside the processingarea). In some embodiments, remote ionization can occur upstream of thedeposition chamber such that ions or other energetic or light emittingspecies are not in direct contact with the depositing film. In somePEALD processes, the plasma is generated external from the processingchamber, such as by a remote plasma generator system. The plasma may begenerated via any suitable plasma generation process or technique knownto those skilled in the art. For example, plasma may be generated by oneor more of a microwave (MW) frequency generator or a radio frequency(RF) generator. The frequency of the plasma may be tuned depending onthe specific reactive species being used. Suitable frequencies include,but are not limited to, 2 MHz, 13.56 MHz, 40 MHz, 60 MHz and 100 MHz.Although plasmas may be used during some of the processes disclosedherein, it should be noted that plasmas may not featured in allembodiments.

One or more of the processes described herein include a purge. Thepurging process keeps the reagents separate. The substrate and chambermay be exposed to a purge after stopping the flow of one or more of thereagents. A purge gas may be administered into the processing chamberwith a flow rate within a range from about 10 sccm to about 10,000 sccm,for example, from about 50 sccm to about 5,000 sccm, and in a specificexample, about 1000 sccm. The purge removes any excess precursor,byproducts and other contaminants within the processing chamber. Thepurge may be conducted for a time period within a range from about 0.1seconds to about 60 seconds, for example, from about 1 second to about10 seconds, and in a specific example, from about 5 seconds. The carriergas, the purge gas, the deposition gas, or other process gas may containnitrogen, hydrogen, argon, neon, helium, or combinations thereof. In oneexample, the carrier gas comprises argon and nitrogen.

According to one or more embodiments, the substrate is subjected toprocessing prior to and/or after forming etch. This processing can beperformed in the same chamber or in one or more separate processingchambers. In some embodiments, the substrate is moved from the firstchamber to a separate, second chamber for further processing. Thesubstrate can be moved directly from the first chamber to the separateprocessing chamber, or the substrate can be moved from the first chamberto one or more transfer chambers, and then moved to a separateprocessing chamber. Accordingly, the processing apparatus may comprisemultiple chambers in communication with a transfer station. An apparatusof this sort may be referred to as a “cluster tool” or “clusteredsystem”, and the like.

Generally, a cluster tool is a modular system comprising multiplechambers which perform various functions including substratecenter-finding and orientation, degassing, annealing, deposition and/oretching. According to one or more embodiments, a cluster tool includesat least a first chamber and a central transfer chamber. The centraltransfer chamber may house a robot that can shuttle substrates betweenand among processing chambers and load lock chambers. The transferchamber is typically maintained at a vacuum condition and provides anintermediate stage for shuttling substrates from one chamber to anotherand/or to a load lock chamber positioned at a front end of the clustertool. Two well-known cluster tools which may be adapted for the presentinvention are the Centura® and the Endura®, both available from AppliedMaterials, Inc., of Santa Clara, Calif. However, the exact arrangementand combination of chambers may be altered for purposes of performingspecific processes as described herein. Other processing chambers whichmay be used include, but are not limited to, cyclical layer deposition(CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD),physical vapor deposition (PVD), other etch, pre-clean, chemical clean,thermal treatment such as RTP, plasma nitridation, degas, orientation,hydroxylation and other substrate processes. By carrying out processesin a chamber on a cluster tool, surface contamination of the substratewith atmospheric impurities can be avoided without oxidation prior todepositing a subsequent film.

According to one or more embodiments, the substrate is continuouslyunder vacuum or “load lock” conditions, and is not exposed to ambientair when being moved from one chamber to the next. The transfer chambersare thus under vacuum and are “pumped down” under vacuum pressure. Inertgases may be present in the processing chambers or the transferchambers. In some embodiments, an inert gas is used as a purge gas toremove some or all of the reactants after forming the layer on thesurface of the substrate. According to one or more embodiments, a purgegas is injected at the exit of the chamber to prevent reactants frommoving from the chamber to the transfer chamber and/or additionalprocessing chamber. Thus, the flow of inert gas forms a curtain at theexit of the chamber.

The substrate can be processed in single substrate deposition chambers,where a single substrate is loaded, processed and unloaded beforeanother substrate is processed. The substrate can also be processed in acontinuous manner, like a conveyer system, in which multiple substrateare individually loaded into a first part of the chamber, move throughthe chamber and are unloaded from a second part of the chamber. Theshape of the chamber and associated conveyer system can form a straightpath or curved path. Additionally, the processing chamber may be acarousel in which multiple substrates are moved about a central axis andare exposed to deposition, etch, annealing, cleaning, etc. processesthroughout the carousel path.

During processing, the substrate can be heated or cooled. Such heatingor cooling can be accomplished by any suitable means including, but notlimited to, changing the temperature of the substrate support andflowing heated or cooled gases to the substrate surface. In someembodiments, the substrate support includes a heater/cooler which can becontrolled to change the substrate temperature conductively. In one ormore embodiments, the gases (either reactive gases or inert gases) beingemployed are heated or cooled to locally change the substratetemperature. In some embodiments, a heater/cooler is positioned withinthe chamber adjacent the substrate surface to convectively change thesubstrate temperature.

The substrate can also be stationary or rotated during processing. Arotating substrate can be rotated continuously or discreetly. Forexample, a substrate may be rotated throughout the entire process, orthe substrate can be rotated by a small amount between exposure todifferent reactive or purge gases. Rotating the substrate duringprocessing (either continuously or discreetly) may help produce a moreuniform deposition or etch by minimizing the effect of, for example,local variability in gas flow geometries.

In atomic layer deposition-type chambers, the substrate can be exposedto the reagents and/or other compounds either spatially or temporallyseparated processes. Temporal ALD (or etch) is a traditional process inwhich the first precursor flows into the chamber to react with thesurface. The first precursor is purged from the chamber before flowingthe second precursor. In spatial ALD (or etch), both the first andsecond precursors are simultaneously flowed to the chamber but areseparated spatially so that there is a region between the flows thatprevents mixing of the precursors. In spatial ALD, the substrate ismoved relative to the gas distribution plate, or vice-versa.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe invention. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the invention.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present invention without departing from the spirit andscope of the invention. Thus, it is intended that the present inventioninclude modifications and variations that are within the scope of theappended claims and their equivalents.

EXAMPLES Example 1—Cobalt Etch (Comparative)

A film of polycrystalline cobalt was provided. The polycrystallinecobalt was etched using Br₂ and N,N,N′,N′-tetramethylethylenediamine(TMEDA). The reagents were present in an amount to result in about 8Angstroms per cycle being etched. A transmission electron microscope(TEM) photograph showing the resulting etched surface is shown in FIG.3A. As can be seen in the figure, the surface was etched at a higherrate at the grain boundaries, leaving valleys at the grain boundaries.

Example 2—Cobalt Etch with Reduced Br₂ Pulse

The etch process of Example 1 was repeated, except that the dose of Br₂was reduced to delivery enough Br₂ to etch about 1 Angstrom per cycle. ATEM photograph showing the resulting etched surface is shown in FIG. 3B.As can be seen in the figure, the boundary effect was significantlymitigated, resulting in a much smoother etch.

What is claimed is:
 1. A method comprising: providing a polycrystallinefilm comprising a transition metal selected from the group consisting ofCo, Cu, Ru, Ni, Fe, Pt, Mn and Pd, the polycrystalline film having acarbon content less than 10% on an atomic basis; exposing thepolycrystalline film to a plasma at a temperature in the range of about23° C. to about 500° C. to amorphize at least a portion of thepolycrystalline film to provide an amorphous region; activating at leasta portion of the polycrystalline film to provide an activated surface;and etching at least a portion of the activated surface by exposing theactivated surface to a reagent comprising a Lewis base or pi acid. 2.The method of claim 1, wherein etching the activated surface comprisescreating a vapor phase coordination complex of the transition metalcoordinated to one or more ligands from the reagent.
 3. The method ofclaim 1, wherein the Lewis base or pi acid comprises a chelating aminerepresented by the structure:

wherein each R^(a) is independently hydrogen or C1-C4 alkyl group withthe proviso that not all of the R^(a) groups are hydrogen.
 4. The methodof claim 3, wherein the chelating amine is selected from the groupconsisting of N,N,N′,N′-tetramethylethylene diamine (TMEDA), ethylenediamine, N,N′-dimethylethylenediamine, 2-(aminomethyl)pyridine,2-[(alkylamino)methyl]pyridine, and 2-[(dialkylamino)methyl]pyridine,wherein the alkyl group is a C1-C6 alkyl group.
 5. The method of claim1, wherein the Lewis base or pi acid comprises CO, PR¹ ₃, wherein eachR¹ is independently a C1-C6 alkyl group,1,2-bis(difluorophosphino)ethane, N₂O, NO, NH₃, NR² ₃, wherein each R²is independently hydrogen C1-C6 branched or unbranched, substituted orunsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic group,or a compound having the structure:

wherein each R^(b) is independently hydrogen, R or C1-C4 alkyl.
 6. Themethod of claim 1, wherein the pi acid comprises AlH_(n)X_(m)R^(c) _(p),wherein X is a halogen, the sum of n+m+p is 3, and R^(c) is C1-C6 alkyl.7. The method of claim 1, wherein activating at least a portion of thepolycrystalline film comprises exposing the polycrystalline film to atransfer agent selected from the group consisting of Cl₂, Br₂ and I₂. 8.The method of claim 1, wherein the polycrystalline film comprisescobalt.
 9. The method of claim 1, further comprising repeatingamorphizing, activating and etching the substrate.
 10. A method ofetching a substrate, the method comprising: providing a polycrystallinefilm comprising cobalt; amorphizing the polycrystalline film by exposingthe polycrystalline film to an inert plasma, reducing gas or reagentvapor at a temperature in the range of about 23° C. to about 500° C.;activating at least a portion of the amorphized polycrystalline film byexposing the amorphized polycrystalline film to a halide transfer agentselected from the group consisting of Cl₂, Br₂ and I₂ to provide anactivated substrate surface; and exposing the activated substratesurface to a reagent comprising a Lewis base or pi acid to provide avapor phase coordination complex comprising one or more cobalt atomscoordinated to one or more ligands from the reagent.
 11. The method ofclaim 10, wherein the Lewis base or pi acid comprises CO, PR¹ ₃, whereineach R¹ is independently a C1-C6 alkyl group,1,2-bis(difluorophosphino)ethane, N₂O, NO, NH₃, NR² ₃, wherein each R²is independently hydrogen C1-C6 branched or unbranched, substituted orunsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic group,or a compound having the structure:

wherein each R^(b) is independently hydrogen, R or C1-C4 alkyl.
 12. Themethod of claim 10, wherein the pi acid comprises AlH_(n)X_(m)R^(c)_(p), wherein X is a halogen, the sum of n+m+p is 3, and R^(c) is C1-C6alkyl.
 13. The method of claim 12, wherein the Lewis base or pi acidcomprises a chelating amine selected from the group consisting ofN,N,N′,N′-tetramethylethylene diamine, ethylene diamine,N,N′-dimethylethylenediamine, 2-(aminomethyl)pyridine,2-[(alkylamino)methyl]pyridine, and 2-[(dialkylamino)methyl]pyridine,wherein the alkyl group is C1-C6 alkyl.
 14. The method of claim 10,wherein the polycrystalline film further comprises one or more metalselected from Cu, Ru, Ni, Fe, Pt, Mn or Pd.
 15. A method comprising:providing a polycrystalline film comprising a transition metal selectedfrom the group consisting of Co, Cu, Ru, Ni, Fe, Pt, Mn and Pd, thepolycrystalline film having a carbon content less than 10% on an atomicbasis; exposing the polycrystalline film to a plasma at a temperature inthe range of about 23° C. to about 500° C. to amorphize at least aportion of the polycrystalline film to provide an amorphous region;activating at least a portion of the polycrystalline film to provide anactivated surface; and etching at least a portion of the activatedsurface by exposing the activated surface to a reagent comprising aLewis base or pi acid comprises one or more of a chelating aminerepresented by the structure:

wherein each R^(a) is independently hydrogen or C1-C4 alkyl group withthe proviso that not all of the R^(a) groups are hydrogen, CO, PR¹ ₃,wherein each R¹ is independently a C1-C6 alkyl group,1,2-bis(difluorophosphino)ethane, N₂O, NO, NH₃, NR² ₃, wherein each R²is independently hydrogen C1-C6 branched or unbranched, substituted orunsubstituted, alkyl, allyl or cyclic hydrocarbon or heteroatomic group,or a compound having the structure:

wherein each R^(b) is independently hydrogen, R or C1-C4 alkyl, or thepi acid comprises AlH_(n)X_(m)R^(c) _(p), wherein X is a halogen, thesum of n+m+p is 3, and R^(c) is C1-C6 alkyl.
 16. The method of claim 15,wherein the chelating amine is selected from the group consisting ofN,N,N′,N′-tetramethylethylene diamine (TMEDA), ethylene diamine,N,N′-dimethylethylenediamine, 2-(aminomethyl)pyridine,2-[(alkylamino)methyl]pyridine, and 2-[(dialkylamino)methyl]pyridine,wherein the alkyl group is a C1-C6 alkyl group.
 17. The method of claim15, wherein activating at least a portion of the polycrystalline filmcomprises exposing the polycrystalline film to a transfer agent selectedfrom the group consisting of Cl₂, Br₂ and I₂.
 18. The method of claim15, wherein the polycrystalline film comprises cobalt.
 19. The method ofclaim 15, further comprising repeating amorphizing, activating andetching the substrate.